There are advantages to classifying a print medium as being recycled paper, glossy paper, or some other media type prior to applying ink to the medium. The classification allows a printer to be set in a print mode which matches the paper, so that a loss of print quality is not incurred. The print mode sets the print parameters, which may influence both the raster image processing techniques and the writing system parameters, such as the number of drops of ink per pixel location, the number of passes by an ink cartridge during the printing process, and the selection of color maps. The classification of the print medium may also reduce the occurrences of damage to a print engine. For example, the coatings on some ink jet transparency films can melt on a fuser roller of commercially available electrophotographic printers, causing damage that requires the fuser roller to be replaced.
Many print drivers allow a user to manually identify the print medium. Thus, a print driver dialog box may be presented to the user to enable selection. However, this ability is often disregarded by users. Instead of selecting a medium from a list of possible media, users may settle for the default setting of the plain paper-normal mode. As a result, even if a user inserts an expensive photo media into a printer, the resulting image is sub-standard when the normal mode is selected.
One possible system for a printer to adopt an optimal print mode for a specific type of incoming media without requiring user intervention utilizes a bar code on a portion of the print medium or on a retainer (e.g., a paper tray) that supports the print medium. U.S. Pat. No. 5,488,223 to Austin et al. describes a system and method of automatically selecting print parameters upon detecting a bar code. A printer includes a bar code scanner which is used to discriminate media types and to set print parameters, such as print speed, printhead pressure, and burn duration.
Another approach for automatically classifying print media types utilizes one or both of sensing transmissivity and sensing reflectivity. For example, a media type detector may be used to sense diffuse and specular reflection, with a pixel size of approximately 40 μm, as measured on the paper. Different media types will have different ratios of the two reflectivity values. To implement the approach, a database having a look-up table of the reflectivity ratios is used to correlate the ratios with the different types of print media.
While the prior art approaches operate reasonably well for their intended purposes, what is needed is an automated method and system for inexpensively distinguishing media types, with a high level of accuracy and a low level of complexity.